The present invention relates to a system for controlling cooling water temperature for an engine mounted on an automotive vehicle and more particularly to a system which controls the temperature of the cooling water to a proper temperature according to load on the engine and conditions of the engine.
Japanese patent publication No. 54-9665 discloses a cooling water control system which is provided with two thermostats for low temperature control and high temperature control and with a valve for controlling the cooling water which is opened in dependency on the load on the engine. The system has disadvantages that the two thermostats occupy a large space. Since the valve is opened in association with the throttle valve of the engine or opened by the vacuum in the intake passage of the engine, the valve is frequently opened during the driving of vehicle. Accordingly, the cooling water often circulates, resulting in excessive cooling of the engine. Therefore, cooling losses increase and thermal efficiency decreases.